+ Location

  • Spinal cord tumors are classified as extradural, intradural-extramedullary, or intramedullary
  • Extradural tumors are most common and account for 50% of spinal tumors
  • Intradural-extramedullary account for 30% and intramedullary account for 15% of spinal tumors

+ Signalment

  • 90% of spinal tumors occur in large breed dogs
  • 28% of spinal tumors occur in cats and dogs < 3 years

Canine Spinal Cord Tumors

+ General Considerations

  • Spinal cord tumors are uncommon in dogs
  • Meningioma is the most common with a predilection for the cervical spinal cord
  • Other primary tumors include LSA, MCT, and intradural-extramedullary spinal cord tumor of young dogs
  • HSA is the most common metastatic tumor, but others include pilomatrixoma and pheochromocytoma

+ Extradural Spinal Cord Tumors

  • Primary vertebral tumors and multiple myeloma
  • Other extradural tumors include myxoma, myxosarcoma, LSA, and lipoma or liposarcoma

+ Intradural-Extramedullary Spinal Cord Tumors

  • Meningioma and peripheral nerve sheath tumors are the most common intradural-extramedullary tumors
  • Spinal meningioma accounts for 14% of all CNS meningioma
  • Spinal meningioma has a predilection for the cervical spinal cord:
  • 40%-77% cervical spinal cord
  • 0%-32% thoracic spinal cord
  • 23%-28% lumbar spinal cord
  • Peripheral nerve sheath tumors involve the spinal cord in 65% cases
  • Other intradural-extramedullary tumors include hemangioma (common), myxoma, myxosarcoma, and an unusual case of diffuse meningeal tumor affecting entire meningeal surface of CNS

+ Intradural-Extramedullary Spinal Cord Tumor of Young Dogs

  • Uncommon
  • Synonyms: ependymoma, neuroepithelioma, spinal cord blastoma, medulloepithelioma, hamartoma, and nephroblastoma
  • Age: 6 months to 3 years
  • Breed predisposition: GSD, Labrador Retriever, and Golden Retriever
  • Clinical signs: lateralized with vast majority of lesions between T10-L2
  • Microscopically similar to nephroblastoma and some believe this tumor may represent extrarenal nephroblastoma arising from ectopic mesonephric or metanephric tissue trapped within the dura during embryologic development
  • Diagnosis: CSF findings are usually non-specific, but albuminocytologic dissociation may be consistent with a chronic neoplastic process
  • Treatment: cytologic reduction or removal associated with long-term survival (4 months and > 3 years) ± radiation therapy for incompletely excised tumors

+ Intramedullary Spinal Cord Tumors

  • Intramedullary spinal cord tumors are uncommon
  • Intramedullary spinal cord tumors usually have glial cell origin: astrocytoma, oligodendroglioma, undifferentiated sarcoma, ependymoma, and choroid plexus papilloma
  • Intramedullary spinal cord tumors are most commonly located between C6-T2
  • Intramedullary spinal cord metastasis can also occur before evidence of the primary tumor
  • Primary tumors with a propensity for metastasizing to the spinal cord include HSA and LSA ± mammary ADC and malignant melanoma
  • Malformation tumors may also affect the spinal cord parenchyma such as epidermoid cyst and hamartoma


+ History

  • Extradural spinal cord tumors are usually slow growing and progressive over weeks to months
  • Acute onset of neurologic signs may be caused by tumor-induced hemorrhage or ischemia
  • Intramedullary tumors have a more rapid growth rate and have a higher incidence of hemorrhage, ischemia, and necrosis

+ Clinical Signs

  • Clinical signs depend on the tumor location and are difficult to differentiate from other causes of myelopathy
  • Extradural tumors may involve the meninges, spinal nerves, or nerve roots which results in varying levels of pain from discomfort to extreme spinal hyperesthesia
  • Tumors involving the brachial or lumbar intumescence may cause lameness, limb elevation, neurogenic muscle atrophy, and depressed spinal reflexes
  • Hyperesthesia is associated with extradural and intradural-extramedullary tumors, but not intramedullary tumors
  • Fundus, lymph node, and rectal examination should be performed for evidence of LSA or metastatic lymphadenopathy


+ Survey Radiographs

  • Thoracic radiographs for evaluation of metastatic disease
  • Radiographic findings include cortical lysis with collapse of the adjacent intervertebral disk space
  • Vertebral body and dorsal lamina are more frequently affected than dorsal and transverse spinous processes
  • Radiographic signs not always visible due to inconsistent vertebral shape, overlying ribs and soft tissue, and improper positioning
  • Cortical bone destruction is a late event in metastatic vertebral lesions
  • Radiographic abnormalities associated with non-vertebral spinal cord tumors are rare, but slow and progressive tumor growth may cause enlargement of an intervertebral foramen or vertebral canal with thinning of cortical bone

alt text From: Withrow SJ & MacEwen EG (eds): Small Animal Clinical Oncology (3rd ed).

+ Cerebrospinal Fluid Analysis

  • CSF collection and analysis are recommended if survey radiographs are inconclusive
  • CSF is collected from a lumbar site and needle left in situ for myelography
  • CSF changes include increased protein content and normal to increased white cell count
  • CSF findings with LSA include increase white cell count with abnormal lymphocytes
  • Abnormal CSF findings are more common in dogs with spinal LSA due to leptomeningeal involvement

+ Myelography

  • Indications: determining presence, anatomical location and dural site of spinal cord tumor
  • Spinal cord tumors are classified as extradural, intradural-extramedullary, or intramedullary
  • Classification may be difficult due to spinal cord edema

alt text alt text From: Withrow SJ & MacEwen EG (eds): Small Animal Clinical Oncology (3rd ed).

+ Advanced Imaging

  • CT is recommended for vertebral tumors due to excellent bone detail
  • However, myelography is superior to CT in differentiating intramedullary from intradural-extramedullary
  • MRI is recommended for spinal cord tumors due to excellent soft tissue detail
  • MRI provides accurate information on anatomic location and bone involvement, but differentiation between intradural, extradural and intramedullary, and extramedullary difficult


+ General Considerations

  • Management options depends on tumor location, extent, and histologic type
  • Aim: alleviate spinal cord compression
  • Treatment options include conservative (with corticosteroids) and surgery
  • Surgery allows decompression ± complete removal or cytoreduction of the mass
  • Surgical decompression techniques include hemilaminectomy and dorsal laminectomy
  • Complete resection of spinal meningioma is complicated by adhesions to the pia mater or spinal cord, and friable texture resulting in piecemeal dissection
  • Rhizotomy can be performed to facilitate tumor resection, but avoided in the brachial and lumbar intumescence
  • Radiation therapy can be used for LSA, incompletely resected spinal tumors, and when surgery is not feasible
  • Spinal cord is resistant to the acute effects of radiation due to low replication rate, but late effects (> 2 years) can be seen due to progressive demyelination and malacia of white matter (especially oligodendrocytes, endothelial cells, astrocytes, and microglial cells)


+ General Considerations

  • Prognosis depends on resectability, histologic type, location, and severity of neurologic signs
  • Poor prognosis for metastatic and vertebral tumors

+ Surgery

  • Guarded to good prognosis for intradural-extramedullary lesions following surgical resection
  • Overall MST 240 days for surgically resected spinal cord tumors:
  • MST 180 days for malignant spinal tumors
  • MST 1,410 days for benign spinal tumors
  • 56% dogs with spinal meningioma alive > 6 months
  • Poor prognostic factors for spinal meningioma include tumors located in either the cervical or lumbar intumescence, ventral tumors, and iatrogenic cord trauma during dissection

+ Radiation Therapy

  • Guarded to good prognosis for intramedullary tumors treated with radiation therapy with normal spinal cord tolerating radiation well and neurologic signs alleviated > 1 year
  • MST 17 month MST for intradural-extramedullary and intramedullary tumors following cytoreductive surgery and radiation therapy